Specifications

Alarms & Diagnostics
3-6 MP2100M-LS-2 Modules - Installation and Operation Manual
Externally Initiated
Local Modem
Loopback - LS-2/M
Only
The external initiated local modem loopback is an ITU-T Rec. V.54 loop 2
performed by the internal channel, in response to the command sent by the
external modem connected to the LS-2/M channel. This loop cannot be
connected by a System Manager command, but its activation is indicated by an
alarm message (EXT INITIATED TEST IN CHn, where n is the channel
number).
When the loopback is activated, the internal modem returns the digital receive
signal toward the external modem via the transmit path.
The loopback signal is shown in figure 3-5.
LS-2/M
I/O MODULES
MTLS-2
I/O MODULES
Local Unit
System
Management
Remote Unit
User or
Test
Equipment
.
.
.
.
.
.
.
.
MODEM
Modem
User or
Test
Equipment
MEGAPLEX
System
MEGAPLEX
System
Figure 3-5. Externally Initiated Local Modem Loopback, Signal Path
Recommended
Test Sequence
The loops available on the LS-2 modules provide a rapid and efficient way to
identify the general location of a fault in an LS-2 module, or in the external
equipment or connections to the module.
If a complaint is received from one of the users connected to an LS-2 module,
first activate the LS-2 local loopback at the side the complaint is received from.
The local user must receive its own signal. If the signal is not received, the
problem is at the local end:
• Check the connections to the user equipment, or the user's equipment itself.
Replace the cable.
• Replace the local LS-2 module.